Position, tilt, and twist detection for stylus

ABSTRACT

A touch-sensitive display device includes a touch sensor having a plurality of display electrodes and control logic coupled to the plurality of display electrodes. The control logic is configured to receive, for each of a plurality of stylus electrodes of an active stylus interacting with the touch-sensitive display device, a spatial capacitance measurement over the touch sensor for that stylus electrode. Relative to the touch sensor, and based on spatial capacitance measurements of the stylus electrodes, the control logic is configured to determine (i) a tip position of the active stylus, (ii) a tilt parameter of the active stylus, and (iii) a twist parameter of the active stylus.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/402,062, filed Jan. 9, 2017, the entirety of which is herebyincorporated herein by reference for all purposes.

BACKGROUND

Touch-sensitive display devices allow users to interact with computerinterfaces using input objects, including fingers, passive styli, activestyli, etc. The touch-sensitive display device may detect a touch eventeach time an input object touches or comes into close proximity with atouch sensor of the touch-sensitive display device. A touch event may beinterpreted by the touch-sensitive display device as a user input at aparticular two-dimensional location relative to the touch-sensitivedisplay device.

Active styli typically include one or more electrodes. These electrodescan be driven with a particular excitation signal to influenceelectrical conditions on a touch sensor, and/or they can be configuredto detect an excitation signal applied to display electrodes of thetouch sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example touch-sensitive display device.

FIG. 2 depicts an optical stack and associated subsystems of thetouch-sensitive display device of FIG. 1.

FIG. 3 depicts an example touch sensor of the touch-sensitive displaydevice of FIG. 1, including a plurality of display electrodes.

FIG. 4 illustrates an example method for a touch-sensitive displaydevice having a touch sensor including a plurality of displayelectrodes.

FIG. 5 schematically shows an example active stylus interacting with atouch sensor.

FIG. 6 schematically shows an example active stylus interacting with atouch sensor.

FIG. 7 schematically shows control logic of an example active stylusdriving stylus electrodes to enable a display-initiated spatialcapacitance measurement.

FIG. 8 schematically shows application of a drive signal to displayelectrodes to enable a stylus-initiated spatial capacitance measurement.

FIG. 9 schematically shows spatial capacitance measurements made duringseveral touch-sensing sub-frames of a single touch-sensing frame.

FIG. 10 schematically shows spatial capacitance measurements for each ofa plurality of stylus electrodes made simultaneously during a singletouch-sensing frame.

FIG. 11 schematically shows determining of a tip position, a tiltparameter, and a twist parameter of an active stylus based on spatialcapacitance measurements.

FIG. 12 schematically shows comparing of spatial capacitancemeasurements received for each of a plurality of stylus electrodes to alibrary.

FIGS. 13A and 13B schematically show correction of an estimated tipposition of an active stylus based on an estimated velocity of thestylus.

FIG. 14 schematically shows an example computing system.

DETAILED DESCRIPTION

As indicated above, a variety of input objects, including passive styli,active styli, and human fingers, can be used to perform touch input at atouch-sensitive display device. However, the touch-sensitive displaydevice is often only capable of detecting the two-dimensional locationof such touch input, and is unable to detect how the input object isangled relative to the display, and also unable to detect when a usertwists the input object. If the touch-sensitive display device were ableto detect this additional information, users could perform moresophisticated input operations, enabling richer and more intuitiveinteraction with the touch-sensitive display device. For example, whiledrawing a line in a software application, the user could change theangle of the input device to change a thickness of the line, whiletwisting of the input device could cause the color of the line tochange.

Accordingly, the present disclosure is directed to detection andinterpretation of touch input provided by an active stylus havingmultiple electrodes in its tip. In some implementations, such an activestylus may include one or more tip electrodes, as well as a ringelectrode encircling the stylus body. Interactions between styluselectrodes of the active stylus and display electrodes of thetouch-sensitive display device results in the touch-sensitive displaydevice receiving spatial capacitance measurements for each styluselectrode of the active stylus. From these spatial capacitancemeasurements, the touch-sensitive display device may calculate a tipposition of the active stylus relative to the display, a tilt parameterof the active stylus, and a twist parameter of the active stylus.

A tilt parameter may include one or more angles specifying theorientation or attitude of the active stylus relative to thetouch-sensitive display device. For example, the tilt parameter mayspecify at what angle the active stylus intersects a plane perpendicularto the display, and/or at what angle the active stylus is “pointing”relative to a coordinate system defined on the surface of the display(i.e., tilt direction in a “north-south-east-west” sense over the planeof the display). Similarly, the twist parameter may define rotation ofthe stylus about an elongate axis extending to the stylus body. Each ofthese values can then be leveraged by software running on thetouch-sensitive display device, and/or any associated computing devices,thereby allowing users to perform more sophisticated touch input.

FIG. 1 shows a touch-sensitive display device 100 including a touchsensor 101. In some examples, display device 100 may be a large-formatdisplay device with a diagonal dimension D greater than 1 meter, forexample, though the display may assume any suitable size. Display device100 may be configured to sense one or more sources of input, such astouch input imparted via a digit 102 of a user and/or input supplied byan input device 104, shown in FIG. 1 as a stylus. Digit 102 and inputdevice 104 are provided as non-limiting examples and any other suitablesource of input may be used in connection with display device 100.Further, display device 100 may be configured to receive input frominput devices in contact with the display device 100 and input devicesnot in contact with the display device 100 (e.g., input devices thathover proximate to a surface of the display). “Touch input” as usedherein refers to both types of input. In some examples, display device100 may be configured to receive input from two or more sourcessimultaneously, in which case the display device may be referred to as amulti-touch display device.

Display device 100 may be operatively coupled to an image source 106,which may be, for example, a computing device external to, or housedwithin, the display device 100. Image source 106 may receive input fromdisplay device 100, process the input, and in response generateappropriate graphical output 108 for the display device 100. In thisway, display device 100 may provide a natural paradigm for interactingwith a computing device that can respond appropriately to touch input.Details regarding an example computing device are described below withreference to FIG. 14.

FIG. 2 is a cross-sectional view of an optical stack 200 of displaydevice 100 of FIG. 1. Optical stack 200 includes a plurality ofcomponents configured to enable the reception of touch input and thegeneration and presentation of graphical output. Optical stack 200 mayinclude an optically-clear touch sheet 202 having a top surface 204 forreceiving touch input, and an optically-clear adhesive (OCA) 206 bondinga bottom surface of the touch sheet 202 to a top surface of a touchsensor 208, which may correspond to touch sensor 101 of FIG. 1, forexample. Touch sheet 202 may be comprised of any suitable material(s),such as glass, plastic, or another material. As used herein,“optically-clear adhesive” refers to a class of adhesives that transmitsubstantially all (e.g., about 99%) of incident visible light.

As described in further detail below with reference to FIG. 3, touchsensor 208 includes a matrix of display electrodes that form capacitorswhose capacitances may be evaluated in detecting touch input. As shownin FIG. 2, the electrodes may be formed in two separate layers: areceive electrode layer (Rx) 210 and a transmit electrode layer (Tx) 212positioned below the receive electrode layer. For example, receive andtransmit electrode layers 210 and 212 each may be formed on a respectivedielectric substrate comprising materials including but not limited toglass, polyethylene terephthalate (PET), or cyclic olefin polymer (COP)film. Receive and transmit electrode layers 210 and 212 may be bondedtogether by a second optically-clear adhesive (OCA) 211. OCA 211 may bean acrylic pressure-sensitive adhesive film, for example.

The touch sensor configuration illustrated in FIG. 2 is provided as anexample, and other arrangements are within the scope of this disclosure.For example, in other implementations, layers 210, 211, and 212 may beintegrally formed as a single layer with electrodes disposed on oppositesurfaces of the integral layer. Further, touch sensor 208 mayalternatively be configured such that transmit electrode layer 212 isprovided above, and bonded, via OCA 211, to receive electrode layer 210positioned therebelow. In general, a touch-sensitive display device willinclude a plurality of display electrodes whose capacitances may beevaluated in detecting touch input, and these electrodes may be arrangedor distributed in any suitable manner.

Receive and transmit electrode layers 210 and 212 may be formed by avariety of suitable processes. Such processes may include deposition ofmetallic wires onto the surface of an adhesive, dielectric substrate;patterned deposition of a material that selectively catalyzes thesubsequent deposition of a metal film (e.g., via plating); photoetching;patterned deposition of a conductive ink (e.g., via inkjet, offset,relief, or intaglio printing); filling grooves in a dielectric substratewith conductive ink; selective optical exposure (e.g., through a mask orvia laser writing) of an electrically conductive photoresist followed bychemical development to remove unexposed photoresist; and selectiveoptical exposure of a silver halide emulsion followed by chemicaldevelopment of the latent image to metallic silver, in turn followed bychemical fixing. In one example, metalized sensor films may be disposedon a user-facing side of a substrate, with the metal facing away fromthe user or alternatively facing toward the user with a protective sheet(e.g., comprised of PET) between the user and metal. Althoughtransparent conducting oxide (TCO) is typically not used in theelectrodes, partial use of TCO to form a portion of the electrodes withother portions being formed of metal is possible. In one example, theelectrodes may be thin metal of substantially constant cross section,and may be sized such that they may not be optically resolved and maythus be unobtrusive as seen from a perspective of a user. Suitablematerials from which electrodes may be formed include various suitablemetals (e.g., aluminum, copper, nickel, silver, gold), metallic alloys,conductive allotropes of carbon (e.g., graphite, fullerenes, amorphouscarbon), conductive polymers, and conductive inks (e.g., made conductivevia the addition of metal or carbon particles).

Continuing with FIG. 2, touch sensor 208 is bonded, at a bottom surfaceof transmit electrode layer 212, to a display stack 214 via a thirdoptically-clear adhesive (OCA) 216. Display stack 214 may be a liquidcrystal display (LCD) stack, organic light-emitting diode (OLED) stack,or plasma display panel (PDP), for example. Display stack 214 isconfigured to emit light L through a top surface of the display stack,such that emitted light travels in a light emitting direction throughlayers 216, 212, 211, 210, 206, touch sheet 202, and out through topsurface 204. In this way, emitted light may appear to a user as an imagedisplayed on top surface 204 of touch sheet 202.

Further variations to optical stack 200 are possible. For example,implementations are possible in which layers 211 and/or 216 are omitted.In this example, touch sensor 208 may be air-gapped and opticallyuncoupled to display stack 214. Further, layers 210 and 212 may belaminated on top surface 204. Still further, layer 210 may be disposedon top surface 204 while layer 212 may be disposed opposite and belowtop surface 204.

FIG. 2 also shows control logic 218 operatively coupled to receiveelectrode layer 210, transmit electrode layer 212, and display stack214. Control logic 218 is configured to drive transmit electrodes intransmit electrode layer 212, receive signals resulting from driventransmit electrodes via receive electrodes in receive electrode layer210, and locate, if detected, touch input imparted to optical stack 200.Control logic 218 may further drive display stack 214 to enablegraphical output responsive to touch input. Two or more control logicsmay alternatively be provided, and in some examples, respective controllogics may be implemented for each of receive electrode layer 210,transmit electrode layer 212, and display stack 214. In someimplementations, control logic 218 may be implemented in image source106 of FIG. 1.

FIG. 3 shows an example touch sensor matrix 300. Matrix 300 may beincluded in touch sensor 208 of optical stack 200 of FIG. 2 to bestowtouch sensing functionality to display device 100 of FIG. 1, forexample. Matrix 300 includes a plurality of display electrodes in theform of transmit rows 302 vertically separated from receive columns 304.Transmit rows 302 and receive columns 304 may be respectively formed intransmit electrode layer 212 and receive electrode layer 210 of opticalstack 200, for example. Each vertical intersection of transmit rows 302with receive columns 304 forms a corresponding node such as node 306whose electrical properties (e.g., capacitance) may be measured todetect touch input. Three transmit rows 302 and three receive columns304 are shown in FIG. 3 for the purpose of clarity, though matrix 300may include any suitable number of transmit rows and receive columns,which may be on the order of one hundred or one thousand, for example.

While a rectangular grid arrangement is shown in FIG. 3, matrix 300 mayassume other geometric arrangements—for example, the matrix may bearranged in a diamond pattern. Alternatively or additionally, individualdisplay electrodes in matrix 300 may assume nonlinear geometries—e.g.,display electrodes may exhibit curved or zigzag geometries, which mayminimize the perceptibility of display artifacts (e.g., aliasing, moirépatterns) caused by occlusion of an underlying display by the displayelectrodes. The transmit rows 302 and receive columns 304 may bepositioned/oriented according to any suitable layout. For example,transmit rows 302 may be oriented horizontally with respect to ground,vertically with respect to ground, or at another angle. Likewise,receive columns 304 may be oriented horizontally with respect to ground,vertically with respect to ground, or at another angle.

Each transmit row 302 in matrix 300 may be attached to a respectivedriver 308 configured to drive its corresponding transmit row with atime-varying voltage. In some implementations, drivers 308 of matrix 300may be driven by a microcoded state machine implemented within afield-programmable gate array (FPGA) forming part of control logic 218of FIG. 2, for example. Each driver 308 may be implemented as a shiftregister having one flip-flop and output for its corresponding transmitrow, and may be operable to force all output values to zero,independently of register state. The inputs to each shift register maybe a clock, data input, and a blanking input, which may be driven byoutputs from the microcoded state machine. Signals may be transmitted byfilling the shift register with ones on every output to be excited, andzeroes elsewhere, and then toggling the blanking input with a desiredmodulation. Such signals are referred to herein as “excitationsequences”, as these signals may be time-varying voltages that, whendigitally sampled, comprise a sequence of pulses—e.g., one or moresamples of a relatively higher digital value followed by one or moresamples of a relatively lower digital value, or vice versa. If the shiftregister is used in this fashion, excitation sequences may take on onlytwo digital values—e.g., only binary excitation sequences can betransmitted. In other implementations, drivers 308 may be configured totransmit non-binary excitation sequences that can assume three or moredigital values. Non-binary excitation sequences may enable a reductionin the harmonic content of driver output and decrease the emissionsradiated by matrix 300.

The drivers 308 may collectively be implemented as drive circuitry 310.Circuitry 310 may be configured to receive commands/inputs from one ormore computer components, for example. Further, circuitry 310 maycoordinate the activation of each driver 308. For example, circuitry 310may establish an order in which each driver 308 is driven, as well asdetermine the signal each driver uses to drive its corresponding row.

In some implementations, matrix 300 may be configured to communicatewith an active stylus, such as active stylus 500 or active stylus 600shown in FIGS. 5 and 6 respectively. This implementation may at leastpartially enable touch-sensitive display device 100 to communicate withinput device 104 when matrix 300 is implemented in display device 100.Specifically, an electrostatic channel may be established between one ormore transmit rows 302 and a conductive element (e.g., stylus electrode)of active stylus 500 or 600, along which data may be transmitted. In oneexample, communication via the electrostatic channel is initiated by thetransmission of a synchronization pattern from matrix 300 to the activestylus. The synchronization pattern may enable matrix 300 and the activestylus to obtain a shared sense of time, and may be transmitted viamultiple transmit rows 302 so that the active stylus can receive thepattern regardless of its position relative to the matrix. The sharedsense of time may facilitate the correlation of a time at which theactive detects an excitation sequence or other signal transmitted ontransmit rows 302 to a location in matrix 300, as the synchronizationpattern may yield an indication of the order in which transmit rows 302are driven.

Each receive column 304 in matrix 300 may be coupled to a respectivereceiver 312 configured to receive signals resulting from thetransmission of excitation sequences on transmit rows 302. The receivers312 may be collectively implemented as receive circuitry 314. Circuitry314 may be configured to process and interpret electrical signalsdetected by the receivers, with the aim of identifying and localizingtouch events performed on matrix 300. During touch detection, matrix 300may hold all transmit rows 302 at a constant voltage except for one ormore active transmit rows along which one or more excitation sequencesare transmitted. During transmission of the excitation sequences, allreceive columns 304 may be held at a constant voltage (e.g., ground).With the excitation sequences applied to the active transmit rows 302and all receive columns 304 held at the constant voltage, a current mayflow through each of the nodes formed by the vertical intersections ofthe active transmit rows with the receive columns. Each current may beproportional to the capacitance of its corresponding node. Hence, thecapacitance of each node may be measured by measuring each currentflowing from the active transmit rows 302. In this way, touch input maybe detected by measuring node capacitance. Matrix 300 may be repeatedlyscanned at a frame rate (e.g., 60 Hz, 120 Hz) to persistently detecttouch input, where a complete scan of a frame comprises applying anexcitation sequence to each transmit row 302, and for each driventransmit row, collecting output from all of the receive columns 304.However, in other examples, a complete scan of a frame may be a scan ofa desired subset, and not all, of one or both of transmit rows 302 andreceive columns 304.

Throughout the present disclosure, touch-sensitive matrices, such asmatrix 300, are generally described as having a plurality of rowelectrodes and column electrodes, with one or more drivers/receiverscoupled to each row/column. However, in some implementations, ratherthan using drive circuitry 310 and receive circuitry 314 to interpretcapacitance in entire rows/columns at once, matrix 300 may beconstructed such that each node (e.g., node 306) comprises a separate,independent display electrode. Accordingly, each node may be coupledwith drive and/or receive circuitry (or other control circuitry/logic)to transmit an excitation sequence to an active stylus and/or receive anexcitation sequence transmitted by an active stylus. It will beappreciated that the touch input detection techniques described hereinare generally applicable regardless of what type of display electrodesare utilized, or how such display electrodes are arranged.

Other measurements may be performed on matrix 300 to detect touch,alternatively or additionally to the measurement of capacitance—forexample, a time delay between the transmission of an excitation sequenceand reception of a received signal resulting from the transmittedexcitation sequence, and/or a phase shift between the transmittedexcitation sequence and the resulting received signal may be measured.

The above-described touch sensor matrix is provided as an example, andis meant to be non-limiting. Other touch sensor configurations may beemployed without departing from the scope of the present disclosure. Ingeneral, a touch sensor matrix will include a plurality of displayelectrodes and control logic coupled to the plurality of displayelectrodes, the control logic usable to detect touch input via theplurality of display electrodes. The specific shape, distribution, andother properties of the display electrodes and control logic can varyfrom implementation to implementation.

As indicated above, and will be further described below, atouch-sensitive display device including a touch sensor matrix, such asmatrix 300, can receive touch input from an active stylus. Interactionsbetween display electrodes of the touch-sensitive display device andstylus electrodes of the active stylus can be interpreted by controllogic of either or both of the touch-sensitive display device and theactive stylus in order to calculate a tip position of the active stylus,a tilt parameter of the active stylus, and a twist parameter of theactive stylus.

FIG. 4 illustrates an example method 400 for detecting touch input inthis manner. At 402, method 400 includes receiving, for each of aplurality of stylus electrodes of an active stylus interacting with atouch-sensitive display device, a spatial capacitance measurement overthe touch sensor for that stylus electrode. “Spatial capacitancemeasurement,” as used herein, refers to a measured capacitance between astylus electrode and a display electrode. The measurement is achievedvia driving one electrode and interpreting resultant electricalconditions at the other electrode (i.e., drive a stylus electrode andreceive at a display electrode, or drive at a display electrode andreceive at a stylus electrode). Typically, the measurement is localizedto a particular two-dimensional position relative to the touch-sensitivedisplay device. The two-dimensional position of the spatial capacitancemeasurement corresponds to the position of a stylus electrode relativeto the display when the stylus electrode was either driven with anexcitation signal that was detected by a display electrode, or detectedan excitation signal from a display electrode.

At 404, method 400 includes determining, relative to the touch sensorand based on the spatial capacitance measurements of the styluselectrodes, (i) a tip position of the active stylus, (ii) a tiltparameter of the active stylus, and (iii) a twist parameter of theactive stylus. This will be illustrated below with respect to FIG. 11.

FIG. 5 shows an example active stylus 500 usable with a touch-sensitivedisplay device incorporating matrix 300 of FIG. 3. As indicated above,interactions between electrodes of stylus 500 and matrix 300 result incontrol logic of the touch-sensitive display device receiving spatialcapacitance measurements, as will be described in further detail below.

Active stylus 500 includes a stylus tip 501 having a first tip electrode502A and a second tip electrode 502B. Active stylus 500 also includes aring electrode 502C. Accordingly, in this example, control logic of thetouch-sensitive display device may receive three spatial capacitancemeasurements corresponding to the three stylus electrodes of the activestylus. In general, a ring electrode may have any suitable size andshape, and may have any position to the active stylus. “Ring electrode”as used herein refers to any electrically conducting structure thatencircles a stylus body.

Active stylus 500 also includes an electrode eraser 504 on an opposingend of the stylus relative to stylus tip 501. It will be appreciatedthat the tip and eraser ends of active stylus 500 may each have anysuitable number of electrodes, though active styli described herein willgenerally have at least one operative end with more than one electrode.The tip electrodes 502 and the electrode eraser 504 may be electricallyconductive and configured to receive current when proximate to a drivenelectrode of electrode matrix 300 of FIG. 3. Active stylus 500 mayinclude a pressure sensor 506 configured to detect a pressure when thetip is pressed against a surface. Likewise, eraser 504 may include apressure sensor 508 configured to detect a pressure when eraser 504 ispressed against a surface. In one example, each of pressure sensors 506and 508 are force sensitive resistors. A touch pressure value of each ofthe respective pressure sensors 506 and 508 may be sent to a controllogic 510. In one example, the touch pressure value may be representedby a 6-bit value.

As shown, tip electrodes 502 and electrode eraser 504 are operativelycoupled to analog circuitry 512. Analog circuitry 512 may include linearanalog componentry configured to maintain the tip/eraser electrodes at aconstant voltage and convert any current into or out of the tip/eraserinto a proportional current-sense voltage.

An analog-to-digital (A/D) converter 514 is operatively coupled toanalog circuitry 512 and configured to digitize voltages received fromanalog circuitry 512 into digital data to facilitate subsequentprocessing. As a non-limiting example, converter 514 may convertincoming electrostatic signals having bandwidths of 100 kHz at asampling rate of 1 Mbit/s.

In the depicted example, active stylus 500 includes a barrel switchbutton 516 that may be operated by a user to provide additional userinput. A depression state of button 516 (e.g., depressed, not depressed,partially depressed) may be sent to control logic 510.

The control logic 510 includes a logic machine 518 and a storage machine520 configured to hold instructions executable by logic machine 518 toperform various operations discussed herein. For example, control logic510 may be configured to receive signals from various sensors includingpressure sensor 506, pressure sensor 508, and button 516. Further,control logic 510 may be configured to process digitized signals fromA/D converter 514 to perform other operations discussed herein.

Via interactions between stylus electrodes 502 of active stylus 500 anddisplay electrodes associated with matrix 300, spatial capacitancemeasurements 522 for each stylus electrode can be localized toparticular two-dimensional locations relative to the touch-sensitivedisplay. This is shown in FIG. 5, in which spatial capacitancemeasurements 522A, 522B, and 522C, corresponding to stylus electrodes502A, 502B, and 502C respectively, are shown at differenttwo-dimensional positions on matrix 300. As will be described in moredetail below, control logic of the touch-sensitive display device mayuse these spatial capacitance measurements to calculate a tip position,tilt parameter, and twist parameter of the active stylus.

FIG. 6 schematically shows an alternative active stylus 500 that can beused in a similar manner to active stylus 500. As with active stylus500, active stylus 600 includes a tip 601, multiple electrodes 602, andcontrol logic 604. In the context of FIG. 6, as well as all subsequentfigures, “control logic” will be used generically to refer to a varietyof processing components of an active stylus, which may include analogcircuitry, an analog/digital converter, a logic machine, and/or astorage machine, as described above with respect to FIG. 5, in additionto any additional suitable componentry. In contrast to active stylus500, active stylus 600 only includes two electrodes at its tip end,including a tip electrode 602A and a ring electrode 602B. Further, ringelectrode 602B is asymmetrical relative to an elongate axis of activestylus 600. Constructing the ring electrode in this manner may allow atouch-sensitive display device to calculate a tip position, tiltparameter, and twist parameter based on spatial capacitance measurementscorresponding to only two stylus electrodes.

As active stylus 600 includes two stylus electrodes, the control logicof the touch-sensitive display device will receive two spatialcapacitance measurements corresponding to the two stylus electrodes ofthe active stylus. These spatial capacitance measurements are shown inFIG. 6 as spatial capacitance measurements 606A and 606B, which havebeen localized to two-dimensional positions relative to matrix 300 andcorrespond to stylus electrodes 602A and 602B respectively.

As indicated above, a capacitance at a particular location relative to atouch sensor may be measured either when a display electrode detects asignal transmitted by a stylus electrode, or a stylus electrode detectsa signal transmitted by a display electrode. Accordingly, localizingspatial capacitance measurements to two-dimensional positions mayrequire only driving display electrodes, only driving stylus electrodes,or some combination of driving both display and stylus electrodes.

Active styli as described herein may therefore be configured to operatein one or both of a receive mode and a drive mode. Further, an activestylus may operate in a hybrid mode, in which one or more styluselectrodes are driven while one or more other stylus electrodes receive.FIG. 7 schematically shows example active stylus 500 operating inreceive mode and interacting with a touch-sensor matrix 700. Receivemode may be employed (1) to synchronize active stylus 500 to thecomputing device/processor associated with the touch-sensor, toestablish/maintain a shared sense of time; and (2) to measurecapacitance at one or more display electrodes 702 of the touch-sensitivedisplay device. Synchronization typically occurs at the beginning of atouch-sensing time frame, in which one or more rows on the touch-sensormatrix are driven with a synchronization pulse that can induce/varyelectrical conditions on one or more stylus electrodes 502 of activestylus 500. The received signal is processed by the control logic,typically via a correlation operation, in order to establish/maintainthe shared sense of timing. Usually, multiple rows, spanning the entireheight/width of the touch-sensor matrix, are driven with thesynchronization pulse so that active stylus 500 receives an adequatesignal regardless of its position relative to touch-sensor matrix 700.

Active stylus 500 may also operate in a receive mode during normaldriving of the display electrodes of touch-sensor matrix 700. Forexample, the control logic of touch-sensor matrix 700 may be configuredto apply a drive signal to each of the plurality of display electrodes702 (e.g., one row at a time), thereby influencing electrical conditionsat one or more stylus electrodes to enable the active stylus tocalculate spatial capacitance measurements. Specifically, control logic510 of active stylus 500 may be configured to detect conditions on oneor more of the first electrode, second electrode, and ring electrodecaused by a drive signal applied from the touch sensor, to enable adisplay-initiated spatial capacitance measurement 704 over the touchsensor. In other words, active stylus 500 may receive signals while therows are scanned to detect when one or more rows proximate to the styluselectrodes of the active stylus are driven, and this detection mayindicate at least one spatial coordinate (e.g., a Y coordinate) of astylus electrode at the time of a spatial capacitance measurement. Insome implementations, both spatial coordinates of the spatialcapacitance measurement may be calculated while the active stylus is inreceive mode, though typically only one spatial coordinate will becalculated.

The receive circuitry typically runs a correlation operation that istuned to the drive signal(s) being used on touch-sensor matrix 700. Uponreceiving a signal of greatest amplitude (e.g., highest correlation),active stylus 500 makes a note of the timing of that highest signal. Therecorded timing allows active stylus 500 and a display device oftouch-sensor matrix 702 to know which row each electrode of activestylus 500 was closest to, thereby providing a Y coordinate of theposition of the electrode relative to the touch-sensitive display devicewhen a capacitance was measured. In other words, spatial capacitancemeasurements received by the control logic of the touch-sensitivedisplay device are calculated by the active stylus based on theelectrical conditions influenced by the drive signal applied to each ofthe plurality of display electrodes.

In some examples, active stylus 500 reports spatial capacitancemeasurements (e.g., timing, value of a row counter) to control logic oftouch-sensor matrix 700 over some type of wireless link (e.g., a radiotransmitter). Accordingly, the control logic may receive the spatialcapacitance measurements calculated by the active stylus via acommunications interface of the touch-sensitive display device. Insteadof or in addition to a radio link, spatial capacitance measurements maybe transmitted electrostatically via excitation of the stylus electrodes502 (or electrode eraser 504) of active stylus 500.

In some implementations, interpolation may be employed to increasepositional resolution. For example, assuming a highest amplitude at rowK, amplitudes may also be noted for rows K−2, K−1, K+1, K+2. Assessingthe amplitudes for these neighboring rows can enable finerdeterminations of the position of the spatial capacitance measurement.Essentially, active stylus 500 “listens” for a communication from rows,and based on the “loudness” of that communication, an assessment is madeas to how close active stylus 500 is to the row that is “talking.” Byassessing communication volume from a few rows on either side of the“loudest” row, a higher position granularity may be determined.

In addition to or in lieu of receiving during a “sync subframe” andduring a “row-drive” subframe, active stylus 500 may drive itselectrodes (tip, ring, or eraser) during a “stylus-drive” subframe. FIG.8 schematically shows active stylus 500 operating in drive mode andinteracting with a touch-sensor matrix 800 having a plurality of displayelectrodes 802. Specifically, control logic 510 of active stylus 500 maybe configured to drive one or more of the first electrode, secondelectrode, and ring electrode to enable a stylus-initiated spatialcapacitance measurement 804 over the touch sensor of the touch-sensitivedisplay device. This may enable calculation of at least one spatialcoordinate (e.g., an X coordinate) of the stylus electrode when aspatial capacitance measurement is taken. Again, in someimplementations, both spatial coordinates of a spatial capacitancemeasurement may be calculated while the active stylus is in drive mode,though typically only one spatial coordinate will be calculated.

As will be described in further detail below, either or both of astylus-initiated spatial capacitance measurement and thedisplay-initiated spatial capacitance measurement may be usable bycontrol logic of the touch-sensitive display device to calculate a tipposition, tilt parameter, and twist parameter of the active stylus. Fromthe perspective of the touch-sensitive display device, the control logiccalculates spatial capacitance measurements for each of the plurality ofstylus electrodes based on electrical conditions detected at one or moredisplay electrodes, the electrical conditions being influenced by thedrive signal applied to the stylus electrodes of the active stylus.Additionally, or alternatively, the active stylus may calculate thespatial capacitance measurements for each of its stylus electrodes basedon electrical conditions influenced by a drive signal applied at one ormore display electrodes, and the active stylus may transmit thecalculated spatial capacitance measurements to the touch-sensitivedisplay device.

Control logic of the touch-sensitive display device may correlate, asdescribed above, in order to interpret the received signals. Forexample, a column experiencing the highest signal, or an above-thresholdsignal, may be deduced to be the column the driven electrode is closestto, thereby establishing the X position of the driven electrode at thetime of the spatial capacitance measurement. And as with the Ydetermination, the conditions at a clustered grouping of columns may beused to establish a higher positional resolution.

In some implementations, spatial capacitance measurements for each ofthe plurality of stylus electrodes may be made separately, duringdifferent touch-sensing subframes of a single touch-sensing frame. Thismay be accomplished when each stylus electrode either is driven with anexcitation signal or detects an excitation signal from a displayelectrode during a different touch-sensing subframe from the otherstylus electrodes. In other words, calculation of the spatialcapacitance measurements may be “time-divided.”

This is schematically illustrated in FIG. 9, which shows a singletouch-sensing frame 900, including three touch-sensing subframes 902A,902B, and 902C. During touch-sensing subframe 902A, stylus electrode502A of active stylus 500 either is driven or is influenced by a drivendisplay electrode, enabling a spatial capacitance measurement 904A to becalculated and localized to a particular two-dimensional position on atouch-sensing matrix. Similarly, during touch-sensing subframes 902B and902C, stylus electrodes 502B and 502C either are driven or influenced bydriven display electrodes, enabling spatial capacitance measurements904B and 904C to be calculated and localized.

In other implementations, during a single touch-sensing frame, spatialcapacitance measurements for each of the plurality of stylus electrodesof the active stylus are made simultaneously in parallel. For example,each stylus electrode may be driven with or configured to detect adifferent excitation signal. Such different excitation signals may insome implementations be orthogonal to one another. In one example,calculation of spatial capacitance measurements may be“frequency-divided” rather than “time-divided.” Measuring spatialcapacitance in this manner can allow for shorter touch-sensing timeframes, and/or allow for more signal integration time during eachtouch-sensing time frame, potentially allowing for more accuratedetection of touch input. However, driving and interpretation ofmultiple simultaneous excitation signals may entail increasedexpense/complexity and, as such, concerns of accuracy and simplicity mayinfluence the particular implementation.

Frequency-divided spatial capacitance measurements are schematicallyillustrated in FIG. 10, which shows a single touch-sensing frame 1000.During touch-sensing frame 1000, all three stylus electrodes of activestylus 500 are driven and/or detect excitation signals from drivendisplay electrodes, allowing three spatial capacitance measurements 1002to be simultaneously calculated and localized on a touch-sensing matrix.

As indicated above, a touch-sensitive display device may be configuredto calculate a tilt position, tilt parameter, and twist parameter of anactive stylus based on spatial capacitance measurements. This isillustrated in FIG. 11, which schematically shows three different views1100A, 1100B, and 1100C of a touch-sensor matrix. In each view of thetouch-sensor matrix, three spatial capacitance measurements 1102corresponding to three stylus electrodes have been localized totwo-dimensional positions relative to the touch-sensor matrix. The threeviews of the touch-sensor matrix are intended to convey how differentrelationships between the two-dimensional positions of the spatialcapacitance measurements can be used by control logic 1104 of thetouch-sensitive display device.

Specifically, view 1100A illustrates how the tip position of an activestylus may be calculated. Based on spatial capacitance measurementsreceived for the first tip electrode and the second tip electrode, thecontrol logic calculates respective positions of the first and secondtip electrodes relative to the touch sensor.

Upon identifying the positions of the first and second tip electrodesrelative to the touch-sensor, these positions are used collectively bycontrol logic 1104 to calculate the tip position 1106 of the activestylus. This may be done by averaging, or otherwise combining, theidentified positions of the two tip electrodes, as depending on thespecific geometry of the active stylus, the position of the stylus tipwill generally be between the positions of the stylus tip electrodes.

View 1100B of the touch-sensor matrix illustrates how a tilt parameterof the active stylus may be calculated. Specifically, upon identifyingwhich spatial capacitance measurements correspond to which styluselectrodes, as described above, control logic 1104 may identify adistance 1108 between a spatial capacitance measurement received for thering electrode, and spatial capacitance measurements received for thefirst and second tip electrodes. Based on this distance, the controllogic may calculate a tilt parameter 1110 of the active stylus. Becausethe ring electrode occupies a known position relative to the stylus tip,the control logic can make use of basic geometric relationships (e.g.,trigonometric functions) in order to calculate the angle at which theactive stylus intersects a plane parallel to the display. The controllogic may optionally calculate the direction the stylus is “pointed”relative to a coordinate system of the touch-sensitive display device bycalculating an angle of a line connecting the detected tip position ofthe active stylus to the spatial capacitance measurement correspondingto the ring electrode.

View 1100C of the touch-sensor matrix illustrates how a twist parameterof the active stylus may be calculated. Specifically, upon identifyingwhich spatial capacitance measurements correspond to which styluselectrodes, as described above, control logic 1104 may calculate theangle of a reference line 1112 running between the respective positionsof the first and second tip electrodes. The angle of this line may beused by the control logic to calculate the twist parameter 1114 of theactive stylus.

The specific operations used to calculate the tip position, tiltparameter, and twist parameter of the active stylus will vary dependingon the number of stylus electrodes in the active stylus, as well astheir orientations relative to one another. For example, control logic1104 may perform different calculations when active stylus 600 shown inFIG. 6 is used, as it includes a single tip electrode and anasymmetrical ring electrode. In this case, the position of the stylustip may simply correspond to the location of the spatial capacitancemeasurement corresponding to the stylus tip electrode. Similarly, thetilt parameter may be calculated based on a distance between the spatialcapacitance measurement for the ring electrode and the spatialcapacitance measurement for the tip electrode. Because the ringelectrode is asymmetrical, the strength of its spatial capacitancemeasurement at a given two-dimensional location on the touch-sensitivedisplay device will vary depending on how the stylus is twisted,allowing the twist parameter to be calculated.

In some implementations, additional or alternative techniques may beused in order to determine a stylus tip position, tilt parameter, andtwist parameter for a given set of spatial capacitance measurements. Forexample, the touch-sensitive display device may include and/or beconfigured to iteratively develop one or more mapping/interpolationfunctions that will output a stylus tip position, tilt parameter, andtwist parameter for a given set of input spatial capacitancemeasurements. Such functions may be developed in a variety of suitableways, and implemented in any suitable hardware, such as, for example,control logic 1104. For example, an active stylus may be applied to thetouch-sensitive display device at a plurality of different positions,with different tilt parameters and twist parameters, and the resultingspatial capacitance measurements may be used to iteratively develop afunction that correctly calculates the output values from the inputmeasurements. This can be done when the touch-sensitive display deviceis manufactured, and/or gradually done as a user uses thetouch-sensitive display device. In some cases, generatinginterpolation/mapping functions as described above may include machinelearning.

In some cases, spatial capacitance measurements received for each of thestylus electrodes may be collectively compared to a library definingdifferent tip positions, tilt parameters, and twist parameters of theactive stylus for each of a plurality of potential spatial capacitancemeasurements. This may be done in addition to or in lieu of calculatingstylus tip positions, tilt parameters, and twist parameters as describedabove. Such a library may be held by a storage machine operativelycoupled with the touch-sensitive display device, for example. In otherwords, each time touch input is detected, the control logic of thetouch-sensitive display device receives a number of spatial capacitancemeasurements in different two-dimensional locations, comprising a uniquepattern or “fingerprint.” The library may have different entries for aplurality of potential spatial capacitance measurements, each differententry specifying a tip position, tilt parameter, and twist parameterconsistent with a pattern of the entry. The control logic may thenaccept the tip position, tilt parameter, and twist parameter for anentry that matches the received pattern as the actual tip position, tiltparameter, and twist parameter of the active stylus.

In one scenario, a library as described above may be generated when thetouch-sensitive display device is manufactured. For example, an activestylus may be applied to the touch-sensitive display device at aplurality of different positions, with different tilt parameters andtwist parameters, and the resulting spatial capacitance measurements maybe stored in the library for future reference. In another scenario, thelibrary may be gradually built as the touch-sensitive display device isused. For example, tip positions, tilt parameters, and twist parametersof an active stylus may be calculated by control logic as spatialcapacitance measurements are received, as described above. As thesevalues are calculated, the control logic may add them to the library,along with the specific pattern of spatial capacitance measurementscorresponding to the calculated values, so that if the same pattern isever observed then the control logic can simply recall the values fromthe library, rather than calculate new values from scratch.

Retrieving tip positions, tilt parameters, and twist parameters asdescribed above is schematically illustrated in FIG. 12, which shows anexample pattern of spatial capacitance measurements 1200 being comparedto a library 1202. Library 1202 includes a plurality of differentpotential spatial capacitance measurements 1204, including at least1204A, 1204B, and 1204C. Each different pattern in library 1202 isassociated with a different record 1206 including a tip position, tiltparameter, and twist parameter associated with the pattern.

As shown in FIG. 12, pattern 1200 corresponds to pattern 1204B oflibrary 1202. Pattern 1204B is associated with record 1206B, whichindicates that the current tip position of the active stylus is “115,130,” which correspond to X and Y coordinates of the stylus tip relativeto a coordinate system defined on the surface of the display, forexample. Similarly, record 1206 indicates that the current tiltparameter of the active stylus is “8, 90,” where “8” may be the angle indegrees at which the active stylus intersects a plane parallel to asurface of the display, and “90” may be the angle in degrees at whichthe active stylus is “pointing” relative to an X axis defined on thesurface of the display. Finally, record 1206B indicates that the twistparameter of the active stylus is “0,” which may be the angle of thediameter of the stylus tip relative to an X axis defined on the surfaceof the display.

As indicated above, measurement of spatial capacitance for each styluselectrode of the active stylus may be “time-divided,” or occur duringdifferent touch-sensing subframes of a single touch-sensing frame. Whenthis is the case, detection of the tip position, tilt parameter, andtwist parameter of the active stylus can be complicated when the activestylus moves in between different touch-sensing subframes. This problemcan be at least partially alleviated by estimating a current velocity ofthe active stylus, and using the current velocity to correct anestimated tip position of the active stylus to a velocity-corrected tipposition.

This is schematically illustrated in FIGS. 13A and 13B. FIG. 13A showsan example touch-sensor matrix 1300, along with the positions of severalstylus electrodes. For the sake of simplicity, touch-sensor matrix 1300is shown as though it is interacting with an active stylus having twotip electrodes and no ring electrodes, though it will be appreciatedthat similar velocity-correction techniques can be applied for activestyli having any number of stylus electrodes.

FIG. 13A shows, on touch-sensor matrix 1300, the actual positions 1302Aand 1302B of two stylus electrodes during a first touch-sensingsubframe. Position 1302A is the detected position of the first styluselectrode, while position 1302B is the actual position of the secondstylus electrode, though this position is not detected during the firsttouch-sensing subframe. FIG. 13A also shows the actual positions 1304Aand 1304B of the two stylus electrodes during a second touch-sensingsubframe, at which time the active stylus has moved to a new position.Position 1304B is the detected position of the second stylus electrodeduring the second touch-sensing subframe, while position 1304A is theactual position of the first stylus electrode during the secondtouch-sensing subframe. However, the first stylus electrode is notdetected at this position, as its position was previously detectedduring the first subframe. Position 1306 in FIG. 13A is the actualposition of the stylus tip during the first touch-sensing subframe,while position 1308 is the actual position of the stylus tip during thesecond touch-sensing subframe. However, from the perspective of thecontrol logic of the touch-sensitive display device, after the secondtouch-sensing time frame, the two stylus electrodes are located atpositions 1302A and 1304B. Accordingly, it may combine these twodetected positions to give an incorrect estimated position 1310 of thestylus tip.

As indicated above, this problem can be at least partially alleviatedwhen an estimated stylus tip position is velocity-corrected. Thisprocess is schematically illustrated in FIG. 13B. By evaluating each ofa plurality of previous touch-sensing frames 1350, control logic of thetouch-sensing display device may estimate a velocity 1352 of the activestylus (e.g., by calculating how far each stylus electrode of the activestylus moves between position detections). The control logic may thencollectively use spatial capacitance measurements made during the mostrecent touch-sensing subframes to calculate an estimated tip position1354 of the active stylus. The control logic may then correct theestimated tip position to a velocity-corrected tip position 1356 basedon the estimated stylus velocity 1352. This may include, for example,multiplying the estimated stylus velocity by the length of eachtouch-sensing subframe to get an offset distance, and adding the offsetdistance to the estimated tip position in a direction matching a vectorof the estimated stylus velocity. In one example, the spatialcapacitance measurements and the estimated velocity vector may be usedcollectively to estimate the tip position directly.

Though FIGS. 13A and 13B focus on using spatial capacitance measurementscorresponding to two stylus electrodes to velocity-correct an estimatedstylus tip position, it will be appreciated that similar operations canbe performed with respect to tilt parameters and twist parameters of theactive stylus. For example, in order to calculate a tilt parameter, thetouch-sensing display device needs an accurate understanding of therelationship between the current stylus tip position and the spatialcapacitance measurement corresponding to the ring electrode, and thismay require that the touch-sensitive display device perform some form ofvelocity correction.

In some embodiments, the methods and processes described herein may betied to a computing system of one or more computing devices. Inparticular, such methods and processes may be implemented as acomputer-application program or service, an application-programminginterface (API), a library, and/or other computer-program product.

FIG. 14 schematically shows a non-limiting embodiment of a computingsystem 1400 that can enact one or more of the methods and processesdescribed above. In particular, computing system 1400 may include orotherwise be usable with a touch-sensitive display device, as describedabove. Additionally, or alternatively, one or more components ofcomputing system 1400 may be implemented on an active stylus thatinteracts with a touch-sensitive display device. Computing system 1400is shown in simplified form. Computing system 1400 may take the form ofone or more personal computers, server computers, tablet computers,home-entertainment computers, network computing devices, gaming devices,mobile computing devices, mobile communication devices (e.g., smartphone), and/or other computing devices.

Computing system 1400 includes a logic machine 1402 and a storagemachine 1404. Computing system 1400 may optionally include a displaysubsystem 1406, input subsystem 1408, communications interface 1410,and/or other components not shown in FIG. 14.

Logic machine 1402 includes one or more physical devices configured toexecute instructions. For example, the logic machine may be configuredto execute instructions that are part of one or more applications,services, programs, routines, libraries, objects, components, datastructures, or other logical constructs. Such instructions may beimplemented to perform a task, implement a data type, transform thestate of one or more components, achieve a technical effect, orotherwise arrive at a desired result.

The logic machine may include one or more processors configured toexecute software instructions. Additionally or alternatively, the logicmachine may include one or more hardware or firmware logic machinesconfigured to execute hardware or firmware instructions. Processors ofthe logic machine may be single-core or multi-core, and the instructionsexecuted thereon may be configured for sequential, parallel, and/ordistributed processing. Individual components of the logic machineoptionally may be distributed among two or more separate devices, whichmay be remotely located and/or configured for coordinated processing.Aspects of the logic machine may be virtualized and executed by remotelyaccessible, networked computing devices configured in a cloud-computingconfiguration.

Storage machine 1404 includes one or more physical devices configured tohold instructions executable by the logic machine to implement themethods and processes described herein. When such methods and processesare implemented, the state of storage machine 1404 may betransformed—e.g., to hold different data.

Storage machine 1404 may include removable and/or built-in devices.Storage machine 1404 may include optical memory (e.g., CD, DVD, HD-DVD,Blu-Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM,etc.), and/or magnetic memory (e.g., hard-disk drive, floppy-disk drive,tape drive, MRAM, etc.), among others. Storage machine 1404 may includevolatile, nonvolatile, dynamic, static, read/write, read-only,random-access, sequential-access, location-addressable,file-addressable, and/or content-addressable devices.

It will be appreciated that storage machine 1404 includes one or morephysical devices. However, aspects of the instructions described hereinalternatively may be propagated by a communication medium (e.g., anelectromagnetic signal, an optical signal, etc.) that is not held by aphysical device for a finite duration.

Aspects of logic machine 1402 and storage machine 1404 may be integratedtogether into one or more hardware-logic components. Such hardware-logiccomponents may include field-programmable gate arrays (FPGAs), program-and application-specific integrated circuits (PASIC/ASICs), program- andapplication-specific standard products (PSSP/ASSPs), system-on-a-chip(SOC), and complex programmable logic devices (CPLDs), for example.

The terms “module,” “program,” and “engine” may be used to describe anaspect of computing system 1400 implemented to perform a particularfunction. In some cases, a module, program, or engine may beinstantiated via logic machine 1402 executing instructions held bystorage machine 1404. It will be understood that different modules,programs, and/or engines may be instantiated from the same application,service, code block, object, library, routine, API, function, etc.Likewise, the same module, program, and/or engine may be instantiated bydifferent applications, services, code blocks, objects, routines, APIs,functions, etc. The terms “module,” “program,” and “engine” mayencompass individual or groups of executable files, data files,libraries, drivers, scripts, database records, etc.

It will be appreciated that a “service”, as used herein, is anapplication program executable across multiple user sessions. A servicemay be available to one or more system components, programs, and/orother services. In some implementations, a service may run on one ormore server-computing devices.

When included, display subsystem 1406 may be used to present a visualrepresentation of data held by storage machine 1404. In some cases,display subsystem 1406 may take the form of a touch-sensitive displaydevice, as described above. This visual representation may take the formof a graphical user interface (GUI). As the herein described methods andprocesses change the data held by the storage machine, and thustransform the state of the storage machine, the state of displaysubsystem 1406 may likewise be transformed to visually represent changesin the underlying data. Display subsystem 1406 may include one or moredisplay devices utilizing virtually any type of technology. Such displaydevices may be combined with logic machine 1402 and/or storage machine1404 in a shared enclosure, or such display devices may be peripheraldisplay devices.

When included, input subsystem 1408 may comprise or interface with oneor more user-input devices such as a keyboard, mouse, touch screen, orgame control logic. For example, input subsystem 1408 may be implementedas a touch sensor including a plurality of display electrodes. In someembodiments, the input subsystem may comprise or interface with selectednatural user input (NUI) componentry. Such componentry may be integratedor peripheral, and the transduction and/or processing of input actionsmay be handled on- or off-board. Example NUI componentry may include amicrophone for speech and/or voice recognition; an infrared, color,stereoscopic, and/or depth camera for machine vision and/or gesturerecognition; a head tracker, eye tracker, accelerometer, and/orgyroscope for motion detection and/or intent recognition; as well aselectric-field sensing componentry for assessing brain activity.

When included, communications interface 1410 may be configured tocommunicatively couple computing system 1400 with one or more othercomputing devices. Communications interface 1410 may include wiredand/or wireless communication devices compatible with one or moredifferent communication protocols. As non-limiting examples, thecommunications interface may be configured for communication via awireless telephone network, or a wired or wireless local- or wide-areanetwork. In some embodiments, the communications interface may allowcomputing system 1400 to send and/or receive messages to and/or fromother devices via a network such as the Internet.

In an example, a touch-sensitive display device comprises: a touchsensor having a plurality of display electrodes; and control logiccoupled to the plurality of display electrodes, the control logic beingconfigured to: receive, for each of a plurality of stylus electrodes ofan active stylus interacting with the touch-sensitive display device, aspatial capacitance measurement over the touch sensor for that styluselectrode; and determine, relative to the touch sensor, and based onspatial capacitance measurements of the stylus electrodes, (i) a tipposition of the active stylus, (ii) a tilt parameter of the activestylus, and (iii) a twist parameter of the active stylus. In thisexample or any other example, the control logic receives two spatialcapacitance measurements corresponding to two stylus electrodes of theactive stylus, including a tip electrode and a ring electrode. In thisexample or any other example, the ring electrode of the active stylus isasymmetrical relative to an elongate axis of the active stylus. In thisexample or any other example, the control logic receives three spatialcapacitance measurements corresponding to three stylus electrodes of theactive stylus, including a first tip electrode, a second tip electrode,and a ring electrode. In this example or any other example, spatialcapacitance measurements received for the first and second tipelectrodes are used by the control logic to calculate respectivepositions of the first and second tip electrodes relative to the touchsensor, and these positions are used collectively by the control logicto calculate the tip position of the stylus. In this example or anyother example, the tilt parameter is calculated by the control logicbased on a distance between a spatial capacitance measurement receivedfor the ring electrode and spatial capacitance measurements received forthe first and second tip electrodes. In this example or any otherexample, spatial capacitance measurements received for the first andsecond tip electrodes are used by the control logic to calculaterespective positions of the first and second tip electrodes relative tothe touch sensor, and the twist parameter of the active stylus iscalculated by the control logic based on an angle of a reference linerunning between the respective positions of the first and second tipelectrodes. In this example or any other example, during a singletouch-sensing frame, spatial capacitance measurements for each of theplurality of stylus electrodes of the active stylus are made separatelyduring different touch-sensing subframes. In this example or any otherexample, the spatial capacitance measurements made during each of thedifferent touch-sensing subframes are collectively used by the controllogic to determine one or more of the tip position, tilt parameter andtwist parameter, and the control logic is further configured to correctone or more of such determinations based on an estimated velocity of theactive stylus. In this example or any other example, the control logicis further configured to apply a drive signal to each of the pluralityof display electrodes, thereby influencing electrical conditions at oneor more stylus electrodes of the active stylus to enable one or more ofthe spatial capacitance measurements. In this example or any otherexample, spatial capacitance measurements received for each of theplurality of stylus electrodes are calculated by the active stylus basedon the electrical conditions influenced by the drive signal applied toeach of the plurality of display electrodes, and the control logicreceives the spatial capacitance measurements calculated by the activestylus via a communications interface of the touch-sensitive displaydevice. In this example or any other example, the control logic isconfigured to calculate spatial capacitance measurements for each of theplurality of stylus electrodes based on electrical conditions detectedat one or more display electrodes, the electrical conditions beinginfluenced by a drive signal applied to one or more of the plurality ofstylus electrodes of the active stylus. In this example or any otherexample, spatial capacitance measurements received for each of theplurality of stylus electrodes are collectively transformed into the tipposition, the tilt parameter, and the twist parameter by an iterativelydeveloped interpolation function.

In an example, a method for a touch-sensitive display device having atouch sensor including a plurality of display electrodes comprises:receiving, for each of a plurality of stylus electrodes of an activestylus interacting with the touch-sensitive display device, a spatialcapacitance measurement over the touch sensor for that stylus electrode;and determining, relative to the touch sensor, and based on the spatialcapacitance measurements of the stylus electrodes, (i) a tip position ofthe active stylus, (ii) a tilt parameter of the active stylus, and (iii)a twist parameter of the active stylus. In this example or any otherexample, the touch-sensitive display device receives three spatialcapacitance measurements corresponding to three stylus electrodes of theactive stylus, including a first tip electrode, a second tip electrode,and a ring electrode. In this example or any other example, receivingspatial capacitance measurements for each of the plurality of styluselectrodes includes applying a drive signal to each of the plurality ofdisplay electrodes, thereby influencing electrical conditions at one ormore stylus electrodes of the active stylus to enable one or more of thespatial capacitance measurements. In this example or any other example,one or more of the spatial capacitance measurements are calculated bythe active stylus based on the electrical conditions influenced by thedrive signal applied to each of the plurality of display electrodes, andthe touch-sensitive display device receives the one or more spatialcapacitance measurements calculated by the active stylus via acommunications interface of the touch-sensitive display device. In thisexample or any other example, receiving spatial capacitance measurementsfor each of the plurality of stylus electrodes includes calculatingspatial capacitance measurements based on electrical conditions detectedat one or more display electrodes, the electrical conditions beinginfluenced by a drive signal applied to one or more of the plurality ofstylus electrodes of the active stylus. In this example or any otherexample, spatial capacitance measurements received for each of theplurality of stylus electrodes are collectively compared to a librarydefining different tip positions, tilt parameters, and twist parametersof the active stylus for each of a plurality of potential spatialcapacitance measurements, and the library is held by a storage machineoperatively coupled with the touch-sensitive display device.

In an example, an active stylus comprises: a stylus tip including afirst tip electrode and a second tip electrode; a ring electrodesurrounding the stylus tip; and control logic coupled to the firstelectrode, second electrode, and ring electrode, the control logic beingconfigured to do one or both of: (a) drive one or more of the firstelectrode, second electrode, and ring electrode to enable astylus-initiated spatial capacitance measurement over a touch sensor ofa touch-sensitive display device; (b) detect conditions on one or moreof the first electrode, second electrode, and ring electrode caused by adrive signal applied from the touch sensor, to enable adisplay-initiated spatial capacitance measurement over the touch sensor;and wherein either or both of the stylus-initiated spatial capacitancemeasurement and display-initiated spatial capacitance measurement areusable to calculate (i) a tip position of the active stylus, (ii) a tiltparameter of the active stylus, and (iii) a twist parameter of theactive stylus.

It will be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. As such, various acts illustrated and/ordescribed may be performed in the sequence illustrated and/or described,in other sequences, in parallel, or omitted. Likewise, the order of theabove-described processes may be changed.

The subject matter of the present disclosure includes all novel andnon-obvious combinations and sub-combinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

1. An active stylus, comprising: a stylus tip including a tip electrode;a ring electrode slanted relative to an elongate axis of the activestylus and forming a continuous ring that encircles a body of the activestylus, such that a portion of the ring electrode is angled toward thestylus tip and a portion of the ring electrode is angled away from thestylus tip; and control logic coupled to the tip electrode and ringelectrode, the control logic being configured to do one or both of: (a)drive one or more of the tip electrode and ring electrode to enable astylus-initiated spatial capacitance measurement over a touch sensor ofa touch-sensitive display device; and (b) detect conditions on one ormore of the tip electrode and ring electrode caused by a drive signalapplied from the touch sensor, to enable a display-initiated spatialcapacitance measurement over the touch sensor; and wherein either orboth of the stylus-initiated spatial capacitance measurement anddisplay-initiated spatial capacitance measurement are usable tocalculate (i) a tip position of the active stylus, and (ii) a tiltparameter of the active stylus, wherein the tilt parameter of the activestylus is derived from a spatial capacitance measurement associated withthe ring electrode.
 2. The active stylus of claim 1, wherein spatialcapacitance measurements for the tip and ring electrodes are localizedto positions over the touch sensor, and wherein the tilt parameter iscalculated based on a distance between the spatial capacitancemeasurement associated with the ring electrode and a spatial capacitancemeasurement associated with the tip electrode.
 3. The active stylus ofclaim 1, wherein either or both of the stylus-initiated spatialcapacitance measurement and display-initiated spatial capacitancemeasurement are further usable to calculate a twist parameter of theactive stylus, and wherein the twist parameter is derived from thespatial capacitance measurement associated with the ring electrode. 4.The active stylus of claim 3, wherein the spatial capacitancemeasurement associated with the ring electrode is localized to atwo-dimensional position over the touch sensor, and the twist parameteris calculated based on a strength of the spatial capacitance measurementassociated with the ring electrode at the two-dimensional position. 5.The active stylus of claim 3, wherein the tip position, tilt parameter,and twist parameter are derived by the by the active stylus andtransmitted to the touch-sensitive display device.
 6. The active stylusof claim 5, wherein the tip position, tilt parameter, and twistparameter are transmitted to the touch-sensitive display device via aradio link of the active stylus.
 7. The active stylus of claim 5,wherein the tip position, tilt parameter, and twist parameter aretransmitted to the touch-sensitive display device electrostatically viaexcitation of one or both of the tip electrode and ring electrode. 8.The active stylus of claim 3, wherein spatial capacitance measurementsfor the tip electrode and ring electrode are collectively transformedinto the tip position, the tilt parameter, and the twist parameter by aniteratively developed interpolation function.
 9. The active stylus ofclaim 3, where spatial capacitance measurements for the tip electrodeand ring electrode are collectively compared to a library definingdifferent tip positions, tilt parameters, and twist parameters of theactive stylus for each of a plurality of potential spatial capacitancemeasurements.
 10. The active stylus of claim 1, wherein the tipelectrode and ring electrode are driven to enable stylus-initiatedspatial capacitance measurements in separate touch-sensing subframes ofa touch-sensing frame.
 11. An active stylus, comprising: a stylus tipincluding a tip electrode; a ring electrode slanted relative to anelongate axis of the active stylus and forming a continuous ring thatencircles a body of the active stylus, such that a portion of the ringelectrode is angled toward the stylus tip and a portion of the ringelectrode is angled away from the stylus tip; and control logic coupledto the tip electrode and ring electrode, the control logic beingconfigured to do one or both of: (a) drive one or more of the tipelectrode and ring electrode to enable a stylus-initiated spatialcapacitance measurement over a touch sensor of a touch-sensitive displaydevice; and (b) detect conditions on one or more of the tip electrodeand ring electrode caused by a drive signal applied from the touchsensor, to enable a display-initiated spatial capacitance measurementover the touch sensor; and wherein either or both of thestylus-initiated spatial capacitance measurement and display-initiatedspatial capacitance measurement are usable to calculate (i) a tipposition of the active stylus, and (ii) a twist parameter of the activestylus, wherein the twist parameter of the active stylus is derived froma spatial capacitance measurement associated with the ring electrode.12. The active stylus of claim 11, wherein the spatial capacitancemeasurement associated with the ring electrodes is localized to atwo-dimensional position over the touch sensor, and the twist parameteris calculated based on a strength of the spatial capacitance measurementassociated with the ring electrode at the two-dimensional position. 13.The active stylus of claim 11, wherein either or both of thestylus-initiated spatial capacitance measurement and display-initiatedspatial capacitance measurement are further usable to calculate a tiltparameter of the active stylus, and wherein the tilt parameter isderived from the spatial capacitance measurement associated with thering electrode.
 14. The active stylus of claim 13, wherein spatialcapacitance measurements for the tip and ring electrodes are localizedto positions over the touch sensor, and wherein the tilt parameter iscalculated based on a distance between the spatial capacitancemeasurement associated with the ring electrode and a spatial capacitancemeasurement associated with the tip electrode.
 15. The active stylus ofclaim 13, wherein the tip position, tilt parameter, and twist parameterare derived by the by the active stylus and transmitted to thetouch-sensitive display device.
 16. The active stylus of claim 15,wherein the tip position, tilt parameter, and twist parameter aretransmitted to the touch-sensitive display device either via a radiolink of the active stylus or electrostatically via excitation of one orboth of the tip electrode and ring electrode.
 17. The active stylus ofclaim 13, wherein spatial capacitance measurements for the tip electrodeand ring electrode are collectively transformed into the tip position,the tilt parameter, and the twist parameter by an iteratively developedinterpolation function.
 18. The active stylus of claim 13, where spatialcapacitance measurements for the tip electrode and ring electrode arecollectively compared to a library defining different tip positions,tilt parameters, and twist parameters of the active stylus for each of aplurality of potential spatial capacitance measurements.
 19. The activestylus of claim 11, wherein the tip electrode and ring electrode aredriven to enable stylus-initiated spatial capacitance measurements inseparate touch-sensing subframes of a touch-sensing frame.
 20. An activestylus, comprising: a stylus tip including a tip electrode; a ringelectrode slanted relative to an elongate axis of the active stylus andforming a continuous ring that encircles a body of the active stylus,such that a portion of the ring electrode is angled toward the stylustip and a portion of the ring electrode is angled away from the stylustip; and control logic coupled to the tip electrode and ring electrode,the control logic being configured to do one or both of: (a) drive oneor more of the tip electrode and ring electrode to enable astylus-initiated spatial capacitance measurement over a touch sensor ofa touch-sensitive display device; (b) detect conditions on one or moreof the tip electrode and ring electrode caused by a drive signal appliedfrom the touch sensor, to enable a display-initiated spatial capacitancemeasurement over the touch sensor; and wherein either or both of thestylus-initiated spatial capacitance measurement and display-initiatedspatial capacitance measurement are usable to calculate a tip positionof the active stylus, and one or both of a tilt parameter of the activestylus and a twist parameter of the active stylus from a spatialcapacitance measurement associated with the ring electrode.